Diaphragm whistle



May 5, 1942. R. L. WILLIAMS DIAPHRAGM WHISTLE Filed Dec. 14, 1937 INVENTOR. ROBERT L;.Wn.:. AMS

ATTORNEY.

Patented May 5, 1942 DIAPHRAGM WHISTLE Robert Longfellow Williams, Newton, Masa, as-

signor to Submarine Signal Company, Boston, Mass., a corporation of Maine Application December 14, 1937, Serial No. 179,734

7 Claims.

The present invention relates to sound producing devices and more particularly to the type generally referred to as diaphragm whistles or horns.

Diaphragm whistles of this type have heretofore been used to a considerable extent and, in general, comprise a metallic diaphragm adapted to be pressed in some manner against a ringshaped opening and to be caused to vibrate by a compressed fluid, such as compressed air. The vibration is often brought about by tensioning the diaphragm in some way against the ringshaped edge, which may be the edge of a horn, or of a chamber open to the atmosphere, compressed air being led to a chamber surrounding or adjacent to the horn chamber in such a way as to force the diaphragm away from the ring shaped edge to permit the air to escape into the horn. This reduces the air pressure in the supply chamber, and the restoring force of the diaphragm again causes it to press against the ring shaped edge, thereby resulting in vibrations of the diaphragm.

Various diificulties have been experienced with this type of horn, particularly in the rapid wearing out and breaking of the diaphragm due to an excessive fiber stress in the diaphragm material. On the other hand, the sound output of such a device has not always been adequate or the vibration frequency has been too low for the desired intensity of sound output.

The present invention provides an improved diaphragm whistle whereby a large sound output can be obtained while not exceeding the safe fibre stress in the diaphragm.

A cross section of a whistle according to the present invention is shown in Fig. 1. Fig. 2 shows diagrammatically a system for employing such a whistle particularly upon submarines. Fig. 3 shows a relief valve of the type used in the system shown in Fig. 2.

In Fig. 1 the flexible diaphragm l of the whistle is clamped in its normal plane and without being under tension within a casing formed in two parts, 2 and 3, and held together by the bolts 4. The right-hand or front part of the casing includes a horn or resonator chamber 5 terminating at its end nearer the diaphragm in an annular edge 6 spaced 8. short distance from the normal diaphragm plane. The member 3 also includes a portion forming with the inner extension of the horn an annular chamber '1 to which air or other fluid under pressure can be admitted by means of the pipe 8 and the restricted. entrance orifice 30. The back half of the casing 2 is conveniently dome shaped and provides a single chamber 12 over the back of the diaphragm or a portion thereof into which air under pressure may be admitted by means of the pipe 9. If desired, the inner side of the member 2 may be provided with a reinforcing rib III which is preferably cylindrical in shape and may terminate in an annular edge ll spaced a suitable short distance from the back of the diaphragm so that it can serve as a stop to limit the backward motion of the diaphragm. This rib is, however, not essential.

In operation, air under pressure is admitted through the pipe 9 into the chamber l2. The pressure is adjusted to be at least suflicient to force the diaphragm l against the annular edge 6. When the whistle is to be sounded, air under pressure is then admitted through the pipe 8 to the chamber 1. The air pressure built up by the chamber 1 must be suflicient to force the diaphragm I away from the annular edge 6 against the back pressure in the chamber l2. The pressure in chamber 1, being assisted by the restoring force of the diaphragm, tends to force the diaphragm back, that is to the left as shown in Fig. 1, beyond its normal position. The air in chamber 1 will, therefore, escape into the horn chamber, thereby reducing the pressure in chamber I. The pressure in chamber l2 plus the diaphragm restoring force-then acts again to press the diaphragm against the ring 6, whereupon the pressure in 'chamber I again builds up. The diaphragm will thus vibrate between positions on both sides of its normal plane.

Since the diaphragm is normally untensioned, its total amplitude of vibration for a given fiber stress can be much higher than in cases where the diaphragm is initially tensioned against the annular ring. Moreover, much higher air pressure can be used in the chamber I, since it is largely balanced by the air pressure in the chamber 12. In this connection it will be appreciated that the actual total pressure applied over the surface of the diaphragm will be very nearly the same on both sides of the diaphragm, although the pressure per unit area will vary due to differences in the sizes of the chambers on opposite sides of the diaphragm. Hence, the amplitude of the diaphragm does not increase with the air pressure used, but can be maintained the same as with lower pressure. Thus the amplitude need never exceed that corresponding to the diaphragmsmaximum safe fiber stress, but with increased pressure the pitch of the sound produced will be increased, since the diaphragms restoring force is increased by the air pressure on both sides of the diaphragm. Moreover, since much greater pressures can be used than heretofore for a given size of whistle, much greater sound output can be obtained.

In order to obtain the maximum sound output for a given air supply pressure, it is desirable that the pressure in chamber l2 be adjustable within fairly close limits. For this purpose, the whistle is preferably connected to the air supply in the manner shown in Fig. 2. Air supplied from a suitable source, such as the tank 13, is conducted to the back chamber l2 of the whistle by means of the pipes l4 and I5, through an adjustable needle valve I6 and pipe 11 to a relief valve l8 and thus into the back chamber l2 of the whistle. If desired, the relief valve l8 may be mounted in the casing wall of the chamber I2 instead of in the supply pipe. A branch l9 from the pipe I4 leads through the whistle valve 20 and a check valve 2| into the front chamber I of the whistle.

The valve I8 is shown in detail in Fig. 3. It comprises a casing 22 defining a chamber 23 having a valve seat engaged by the valve 24. To close the orifice 25 leading from the supply pipe 26, the valve 24 is held against its seat by the spring 21 whose tension is variable by the thumb screw 28. An opening 29 in the valve casing 22 permits air which flows into the valve chamber 23 from the supply pipe 26 to escape to the outer atmosphere. It will now be evident that when the pressure in the supply pipe 26, applied to the base of the valve 24, exceeds the force of the spring 21, the valve will open, permitting some air to escape into the chamber 23 and through the orifice 29, whereby the pressure in the pipe 26 is maintained substantially constant, 1. e., disregarding pressure fluctuations occasioned by the vibration of the diaphragm since the supply pressure is, of course, always greater than the pres-' sure in chamber i2. In other words, while the valve 24 by itself merely serves to maintain constant in chamber l2 the predetermined maximum pressure to which the valve is set it, together with a source of supply whose pressure is always greater than that predetermined maximum pressure, at which valve 24 opens, serves to maintain the pressure in whistle chamber l2 at a substantially constant value.

Now, referring again to Fig. 2, in order to properly set the various valves in the system and to produce maximum response of the horn, the needle valve I6 is first opened permitting pressure to build up in the back chamber l2 of the whistle. The'whistle valve 20 is then opened causing the diaphragm to vibrate. Adjustment of the relief valve I8 is then made until the pressure in chamber I2 is such that the sound emitted by the whistle is of maximum intensity. If the chamber I2 has much greater surface in contact with the diaphragm than the chamber 1, considerable air will be escaping from the valve I! when the proper adjustment has beenmade. The needle valve I6 is, therefore, provided to reduce the flow of air supplied to the pipe I], whereby very little, if any, air is wasted through the valve IS in maintaining correct pressure in the chamber l2.

It is important to note that the provisionof means for adjusting the pressure in the back chamber l2 makes it possible to obtain the greatest sound output from a whistle of fixed parameters, such as diaphragm size and thickness and entrance orifice 30 to the chamber I, regardless of the air pressure which may be available. A

limit is reached, of course, when the pressure of the air supply is so high that the flow of air into the horn is greater than can be dissipated. In this case it is necessary to reduce the air supply to chamber 1 in a suitable manner as by employing a smaller entrance orifice.

The arrangement shown in Fig. 2 is not only useful in the ordinary whistle installation, but is particularly advantageous in the event that the whistle is to be mounted on the deck of a submarine where it will be subject, when submerged, to very large water pressure. The water entering the horn 5 will tend to force the diaphragm surface away from the ring 6 and to enter the pipe 8 leading to the check valve 2|. The latter prevents any further rogress of the water. However, the water pressure may well be great enough to tend to burst the diaphragm. However, the relief valve l8, which is also installed on the deck of the submarine, is, when submerged, also subject to the water pressure. The water entering the valve chamber 23 through the aperture 29 increases the pressure upon the valve 24 and thereby permits the air pressure in the pipe 26, and consequently in the chamber l2 of the whistle, to build up'above the water pressure. The pressure in the supply tank normally is greater than the pressure of the water when the submarine is fully submerged and consequently there will be no danger of breakage of the diaphragm by the water pressure.

Having now described my invention, I claim:

1. A diaphragm whistle comprising a casing, a flexible diaphragm mounted in said casing, a fluid pressure chamber on one side of said diaphragm, a horn chamber open to the atmosphere on the same side of said diaphragm having a passage communicating with said first chamber, said passage being adapted to be opened and closed by the vibration of the diaphragm, a fluid pressure chamber permanently closed to the outer atmosphere on the opposite side of the diaphragm formed in part thereby, whereby fluid pressure in the latter chamber acts directly on the diaphragm and means for supplying fluid under pressure greater than atmospheric to both fluid pressure chambers.

2. A diaphragm whistle comprising a casing, a flexiblediaphragm clamped at its periphery within the casing and adapted to vibrate between extreme positions on each side of its normal untensioned position, a horn chamber open to the atmosphere and having an inner annular surface concentric with the diaphragm at the front side thereof and spaced from the normal diaphragm position but so as to be contacted by the diaphragm in one of its extreme vibrating positions, a fluid pressure chamber at the front side of the diaphragm communicating with said horn chamber by way of the space between said annular surface and said diaphragm and a chamber permanently closed to the outer atmosphere adapted to be supplied with fluid under pressure at the back side of the diaphragm and formed in part thereby so that the fluid pressure in this chamber acts directly on the diaphragm and means independent of vibration of the diaphragm for conducting fluid under pressure to both of to the outer atmosphere by the diaphragm when the latter is in one of its extreme positions and to be open at all other diaphragm positions, a-

chamber at the other side of the diaphragm formed in part thereby and permanently closed to the external atmosphere, means for applying to the second chamber fluid under pressure at least sufficient to force the diaphragm into its extreme position closing said first chamber and means for applying to the first chamber fluid under pressure suflicient to open said first chamber against the pressure in the second chamber.

4. A diaphragm whistle for use on the exterior of a submarine including a flexible diaphragm, means supporting the same at its periphery, a substantially closed chamber covering substantially the whole of the back side of the diaphragm, a chamber on the front side of the diaphragm covering only a portion of its surface adapted to be opened and closed by the vibrations of the diaphragm, a remaining portion of the diaphragm on its front side being exposed to the outer medium, a source of fluid under pressure greater than the water pressure at maximum submergence, means for conducting said fluid to both chambers and means responsive to submergence of the submarine for maintaining the pressure in the back chamber substantially constant at a value below the pressure of the source when above the water surface and when submerged increasing the pressure in the back chamber acting on the diaphragm to an amount greater than the external water pressure act diaphragm.

5. A diaphragm whistle comprising a casing, a flexible diaphragm clamped at its pheriphery within the casing and adapted to vibrate between extreme positions on each side of its normal untensioned position, a horn chamber open to the atmosphere and having an inner annular surface concentric with the diaphragm at the front side thereof and spaced from the normal diaphragm position but so as to be contacted by the diaphragm in one of its extreme vibrating positions, a fluid pressure chamber at the front side of the diaphragm communicating with said horn chamber by way of the space between said annular surface and said diaphragm, a closed chamber adapted to be supplied with fluid under pressure at the back side of the diaphragm,a supply of fluid under pressure greater than a predetermined ng on the front of the minimum value, means independent of vibration of the diaphragm for conducting the fluid to both pressure chambers and valve means communicating with said closed chamber for maintaining the fluid pressure therein at a predetermined maximum value less than saidfluid supply pressure.

6. A diaphragmwhistle comprising a casing, a-

fiexible diaphragm clamped at its periphery within the casing and adapted to vibrate between extreme positions on each side of its normal untensioned position, a horn chamber open to the atmosphere and having an inner annular surface concentric with the diaphragm at the front side thereof and spaced from the normal diaphragm position but so as to be contacted by the diaphragm in one of its extreme vibrating positions, a fluid pressure chamber at the front side of the diaphragm communicating with said horn chamber by way of the space between said annular surface and said diaphragm and a closed chamber adapted to be supplied with fluid under pressure at the back side of the diaphragm, a supply of fluid under pressure, means independent of vibration of the diaphragm for conducting the fluid to the front chamber, means independent of vibration of the diaphragm for conducting the fluid to the back chamber, valve means communicating with the back chamber for maintaining the pressure therein at a predetermined maximum value and means for adjusting said valve to adjust said maximum value to the point where maximum sound output is obtained. 7

7. A diaphragm whistle comprising a casing, a flexible diaphragm mounted in said casing, a fluid pressure chamber on one side of said diaphragm, a horn chamber on the same side of said diaphragm having a passage communicating with said first chamber, said passage being adapted to be opened and closed by the vibration of the diaphragm, a closed fluid pressure chamber on the opposite side of the thereby, whereby fluid pressure in the latter chamber acts directly on the diaphragm, means independent of vibration of the diaphragm for supplying fluid under pressure to both fluid pressure chambers and means for adjusting the maximum pressure supplied to said second chamber independently of the pressure supplied to said flrst chamber.

ROBERT LONGFELLOW WILLIAMS.

diaphragm formed in part 

